Electric switch



Feb. 27, 1934.

H. B. LAw'roNy w 14,948,938

ELECTRIC SWITCH Filed Feb. 1, i955 /aff l v /l v k l l f HARVEY @.L/,WTQA/ ATTORNEYS.

Paternal Feb. 27, 1934 UNITED STATES" viril-:lar-v OFFICE Application February 1, 1933. Serial No. 654,565

1 Claim.

This invention relates to improvements in electric switches and more particularly to the type known as thermal or heat switches.

It is an object of thisinvention to provide a heat switch in which both of the contact members are formed of thermostatic or bi-metallic metal so that when the switch is closed, both contact members respond equally and simultaneously to changes in the temperature of the surrounding atmosphere whereby the switch remains closed irrespective ofthe degree of atmospheric changes.

With these and lother objects in view, reference is made to the accompanying sheet of drawing with the understanding that minor detail changes may be made without departing from the scope i thereof.

In the drawing;

Figure 1 is a top plane view of an embodiment of this switch.

Figure 2 is a view in front elevation showing the position assumed by the parts when the circuit therethrough is broken.

Figure 3 is a view partly in section and partly in plane taken on the line 3-3 of Figure 2 looking in the direction of the arrows.

Figure 4 is a view similar to Figure 2 illustrating the position assumed by the parts when the circuit is closed throughv the switch.

In the embodiment of this invention a heating element 1, preferably formed of a strip oi insulation material with a wrapping of resistance wire thereabout, is mounted at each end upon metallic brackets 2 and 3 in turn securedupon the panel 4 of insulation material. A switch member 5 comprising a strip of thermal or bi-metallic metal is secured at one end to the metallic bracket 6 mounted upon the panel 4 normally supporting the switch member in parallel relation to the heating element 1. A similarly constructed switch member '7 of thermal or bi-metallic metal is secured at one end to a metallic bracket 8 mounted upon the panel 4 directly below the bracket 6. The bracket is connected by a binding post passing through the panel 4 to an electrical connector 9. The bracket 2 is similarly connected to an electric connector 10 upon the opposite side of the panel 4.

The free end of the switch member 5 mounts upon the upper side a contact member 11' and upon the lower side a shouldered insulating block 12. The free end of the lower switch member 'I mounts a spring arm 13 terminating in a contact 14 normally adapted to engage the contact 11 upon the upper arm 5 as shown in Figure 4 and upon upward movement of the contact l1 is (Cl. 20D-122) f adapted to slide thereunder and engage the shouldered insulating block 12.

A lead 15 connects the bracket 6 with the bracket 3 which latter bracket is connected to one end of the resistance wire coiled about the 0 heating element 1, the other end of said wire being connected to the bracket 2. It is therefore seen that when the electric contactors 9 and 10 are connectedvin a 'circuit and the switch elements are in a 'position as shown in Figure 4, the 65 current will ow through bracket 9, switch member '7, spring 13, contact 14, contact 11, switch member l5, bracket 6, lead 6, bracket 3, through the resistance wire of the heating element to bracket 2 completing the circuit. As current 70 passes through the resistance element, heat will be produced which will be imparted to the bimetallic switch member 5 to cause the free end to move in an upward direction until finally the 'contact 1l is moved out of engagement with the contact 14 'whereupon the contact 14 will be caused by the spring 13 to slide under and engage the shouldered insulating block 12, thereby breaking the circuit and maintaining the circuit breaking of the circuit, the heating element will cool and the switch member 5 will tend to againy resume itsparallel relationship to the heating element and in so doing, will maintain the contact 14 in engagement with the insulation block 12.

The member 7 is mounted in parallel relation to the member 5 and at a suiiicient distance from the heating element 1 to be sufllciently removed from the heat eminating therefrom as not to be substantially affected thereby.

It has been found in switches of this character that a bi-metallic strip carrying a contact will respond to changes in the temperature of the surrounding atmosphere so that upon an increase in temperature, the contact carrying switch arm may be deformed suiciently to break the contact when it is not desired.v It has also been found that by constructing the other contact varm 'I of a similar strip of bi'metallic metal and mounting it substantially parallel to the first arm, upon any decided change in temperature of the' surrounding atmosphere, both arms will respond simultaneously and thereby maintain their parallel relationship with the results that the contacts v`wil1 remain closed until the arm 5 is caused to 105 member 'I with a spring 18 in engagement with a pin 19 to normally maintain the plunger in its extended position but allow upon depression of the plunger, the end adjacent the spring member 13 to engage said member, when the switch has been opened, and move it away from the shouldered insulating block 12 to allow the contact 11 to drop down so that upon the release of the plunger, the contact 11 will engage the contact 14 against the tension of the spring 13 and close the circuit.

What I claim is:

An electric thermal switch including two similar spaced apart bi-metallic contact carrying arms fixed at their corresponding ends to binding posts supporting said arms in parallel relation to each other irrespective of changes in atmospheric temperature, a contact mounted upon the free end of one arm and extending therebeyond with a shouldered insulating block secured upon the underside thereof terminating short of the exterior end of said contact, a spring member carrying a complementary contact and extending therebeyond mounted on the end of the other arm, said contact adapted to be engaged on one side by the end oi' the contact extending beyond the first arm, said spring member normally maintaining said contacts in engagement, an electric heating element adjacent the rst arm connected in series with the binding post of said arm in said switch circuit adapted when energized to cause the rst arm to deform and move upward out of engagement with the spring carried con.- tact whereupon said spring causes the contact carried thereby to engage the shouldered insulating block and maintain the contacts separated, a spring pressed plunger mounted between said arms adapted upon depression to engage the contact carrying spring and move it outward allowing the first contact to resume its normal position and upon release of. the plunger engage the side of the second contact.

HARVEY B. LAWTON. 

